Field of the Invention
The invention relates to the field of conveying technology, for example for piece goods, in particular singularised piece goods. It relates to a conveying system with conveying sections and to a method for the regulation (closed-loop control) of drives of conveying sections of the conveying system, according to the preamble of the respective independent patent claims.
Description of Related Art
Conveying devices with conveyors for the singularised conveying of products, for example printed products such as newspapers, pamphlets, brochures as well as collections of these are known. With this, a product in each case is conveyed in a manner separately from the others, thus individually, wherein the products are held by grippers, or lie in pockets or on saddles or on conveying belts. Such conveyors can extend over a conveying stretch of up to several hundred meters. They can have distributed drives, wherein the power of the drives is designed according to the course of the respective conveyor. Transfer conveyors can be applied for the transfer of products between conveyors. Their movement must be synchronised with the movement of the conveyors, so that the products can be transferred individually. This can be effected by way of a centralised, superordinate control or a clock setting. This however increases the complexity of the control as well as the effort with regard to programming and starting operation of the control.
EP 2 130 103 B1 describes a drive control system for a conveying belt. A balanced introduction of force and regulation of the speed is to be rendered possible. For this, a loading of the conveying belt is measured and necessary drive moments for several drives are centrally computed by way of a dynamic chain pull computation software. The loading (load) is measured by way of counting how many chain links are located in a given section, or by way of detecting where individual conveyed products are located along the conveying path. It must, therefore, be known as to how an individual product affects the loading of the belt, and moreover in dependence on whether the belt runs horizontally or ascends or descends. A central control is also present, and this must have information regarding all sections of the conveying belt.
DE 102 45 323 B4 discloses a method for determining the speed of a chain link belt. Thereby, a characteristic of the belt is constantly measured at two locations, past which the belt runs. The measurement signals are correlated to one another, by which means a temporal offset results, and, from this, the speed of the belt.
DE 20 2012 003 907 U1 describes a monitoring system for tensile and compressive forces in a chain serving for leading cables, hoses and likewise in a protected manner. An element for measuring these forces is arranged on a moved end of the chain for this. The element is designed as a cantilever and includes sensors for measuring its deformation.
DE 201 21 622 U1 discloses a conveying chain that has microsensors on the chain links for the purpose of monitoring. The microsensors, for example, include strain gauges, as well as data memories and means for the wireless data transmission to an external measurement data evaluation.
DE 203 19 743 U1 shows a control device for monitoring the mechanical tension of a saw chain. The tension can be measured by way of a spring-loaded lever engaging below the saw chain.
GB 1 524 971 discloses the regulation, which is to say servo control or closed loop control, of a conveying system with several drives. Each drive has a speed regulation. Each speed regulation receives a command signal from a superordinate torque regulation, in order to regulate the torque of the associated drive to a torque reference value. The torque reference value for several slave drives is equal to the actual torque of a master drive. The measurement of the torque of each drive is effected by way of a measurement of the current for feeding the drive. The speed is measured by a tachogenerator on the drive shaft.
WO 2102/060999 concerns itself with the damping of oscillations of an elastic conveying belt. Distributed drives are applied for this, and these, although serving primarily for damping oscillation, however can also serve for assisting a main drive. The oscillations are measured by acceleration sensors that run along on the belt, for example in three orthogonal directions. A regulation zone along the belt is assigned in each case to a drive controller. Acceleration sensors in a regulation zone transmit their measurements to a controller for this zone in each case.
EP 2159655 describes a centralised control of distributed controllers in a conveying system. The emphasis of the application relates to the communication between these controllers. One speaks of a load sensor and of a load height sensor, which are reflective-type sensors. It is obviously the case of sensors that detect the presence of a transported object (load), which is the load status.
JP S5733115 in a manner similar to the above-mentioned EP 2159655 appears to describe a conveying device, where individual sections are controlled according to the presence of conveyed objects, i.e. they are switched on given the presence of an object and switched off again after its conveying.
DE 102007006839 shows a conveying device with several conveying sections. Each conveying section has several drives that can be connected and disconnected. The speed of the drives is load-dependent. Regulated drives are mentioned as belonging to the state of the art and are assessed as requiring too much effort. The load (e.g. the slump of the speed at a high load) is measured at a drive which is considered as a master, and one or more further drives in the same conveying section are accordingly switched on or off
DE 19921165 shows a conveying system with a belt drive. In consecutive sections, the movement in a section is stopped in each case by a pneumatic drive, if the presence of an article is detected in the subsequent section.
DE 19644092 shows how a chain tension is measured with deflection roller at one or more locations in a circulating conveyor with several drives. The speed of the drives is accordingly adapted.